Preventing emboli from entering the carotid arteries (i.e., the brachiocephalic, the left common carotid, and the left subclavian) by way of the aorta reduces the incidence of ischemic stroke. Emboli in the aorta come from several sources. These sources include: 1) aortic atheroma which detaches from the wall of the aorta due to various reasons including incising, clamping, and/or clamp release of the aorta during surgery (see, Barbut et al., "Cerebral Emboli Detected During Bypass Surgery Are Associated With Clamp Removal," Stroke, 25(12):2398-2402 (1994)); 2) thrombus which forms in the right atrium resulting from atrial fibrillation; 3) thrombus which forms on ventricular assist devices; 4) venous thrombus which passes into the left ventricle through a patent foramen ovale or other arteriovenous shunt; and 6) other less common sources.
There are a number of known devices designed to filter blood (see, e.g., Barbut et al., International Application No. PCT/US97/1275 1, and Barbut et al., U.S. Pat. No. 5,662,671), but no known devices designed to divert or redirect emboli past the carotid arteries. Using careful surgical techniques, the chance of an embolic event causing harm to the patient by way of cerebral embolization is so low that emboli managing devices have not been considered. Thus, there are no known solutions to minimizing the probability of cerebral embolization, except for reducing the amount of emboli released into the blood stream by careful handling of blood vessels.
On the venous side of the circulatory system, implantable vena cava filters reduce the incidence of pulmonary embolism, but they only trap large emboli, and they have a tendency to become clogged as they accumulate material. For example, Cottenceau et al., U.S. Pat. No. 5,375,612 discloses a blood filter intended for implantation in a blood vessel, typically in the vena cava. This device comprises a zigzagged thread wound on itself and a central strainer section to retain blood clots. Another example is Lefebvre, French Patent No. 2,567,405, which discloses a blood filter for implantation by an endovenous route into the vena cava. The filtering means may consist of a flexible metallic grid, a flexible synthetic or plastic grid, a weave of synthetic filaments, or a nondegradable or possibly biodegradable textile cloth.
There are very few intravascular devices designed for arterial and especially aortic filtration, much less diversion. A filter that functions in arteries must address additional concerns because of the hemodynamic differences between arteries and veins. Arteries are much more flexible and elastic than veins and, in the arteries, blood flow is pulsatile with large pressure variations between systolic and diastolic flow. These pressure variations cause the artery walls to expand and contract. Thus, filters and diverters must be able to expand and contract along with the lumen of the aorta to which they may be anchored.
The problem of preventing emboli from reaching the cerebral vasculature has thus far not been adequately addressed. Therefore, a need exists for new devices and methods to prevent embolic material from entering the carotid/cerebral arteries, while maintaining peripheral blood flow from the heart to the descending aorta.